As it is known in the optical communications art, light signals can be modulated in accordance with associated data signals such that the information is optically conveyed between transmitter and receiver devices. In order for that optical data to be efficiently transmitted, each of the intervening optical components should be in a precise, optimal alignment. Such alignment is typically achieved by transmitting an exemplary light beam through the optical components. As the light beam exits the arrangement of optical components, a measurement is performed of its parameters such as power or spectrum for instance. The optical components can be subsequently moved in relation to each other until an optimum combination of the output light parameters is attained. The process usually has many steps and is fairly slow. Sometimes the duration of the process becomes prohibitive to large volume manufacturing. It is especially true when three or more dimensional alignment is required.
Once an optimal alignment of the optical components is achieved, the components are fixed in place using a variety of methods. One of those methods, that is widely used, includes the use of ultra-violet (UV) curable epoxy. The epoxy is disposed on a portion of each component which will enable it to be rigidly fixed to a substrate or other structure. The UV source is subsequently turned on until the epoxy has cured. It is readily apparent that the optical components must remain precisely fixed until the epoxy has cured. It is also important to keep the epoxy layers as thin as possible to minimize the influence of the epoxy shrinkage during cure on the optical alignment.
A system is needed that allows fast and precise three-dimensional alignment of components and also allows the components to be held motionless while the epoxy is cured.
In accordance with an aspect of the present invention, a method and apparatus are provided for optimally aligning a number of optical components in three dimensions.
More specifically, a method is disclosed that is initiated by fixing one of the optical components at a selected location on a semiconductor substrate. Subsequently, the other optical component and its associated submount are attached to a pair of coupled motion stages. A reference light beam, to which the first optical component has been aligned, is transmitted to the other component and to a detector. That detector is positioned to measure changes in a selected characteristic of the reference signal, such as changes in optical power, as the position of the second optical component is manipulated. Through the use of a feedback loop, the second component and submount are moved in a pattern until an optimal alignment is converged upon.
In accordance with another aspect of the invention, the detector monitors a characteristic of the reference signal and, based upon that measurement, a determination is made regarding the location of the optical component which maximizes that characteristic. That process is repeated while the distance between the components is changed until optimal alignment is achieved.
In accordance with a further aspect of the invention, the optical component and its associated submount are fixed on the device substrate at the point of optimal alignment.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.